Did you do
Code:
# cat /proc/pci

  Bus  0, device  10, function  0:
    Communication controller: PCI device 151f:0000 (TOPIC SEMICONDUCTOR Corp) (rev 0).
      IRQ 12.
      I/O at 0xbc00 [0xbc07].
This is on the same site you use. And this is from another forum:
"The 5610B works with Mepis 2004.06 and SM 3.3. I did nothing special. But you have to make sure you have it on the correct COM Port for your machine. Sometimes u have to confirm the com port via windoz - I hate to say that. You may have to link the port to /dev/modem.

Alternatively, try ls -l /dev/modem to find out the com port. You can also do things like ls -l /dev/ttyS2, etc. All from Command line. The latter gives the c 4 68 part of it. Also see man pages on ls. Watch the spaces in the code.

Two other handy pieces of code, from cmnd line as su:

mknod /devttyS2 c 4 68 Here S2 is COM3, etc.
(this sets S2)

ln -s /dev/ttyS2 /dev/modem Links e.g. S2 to /dev/modem"